Nucleic acids and nucleotides Flashcards
3 components of the nucleotide
- The base
- The sugar
- The phosphate
RNA and DNA
Ribonucleotides for RNA and Deoxyribonucleotides for DNA
Nucleotides are abbreviated
as nitrogenous bases and are indicated as letters of the code
Nucleoside vs nucleotide
both fundamental building blocks in nucleic acids but differ in structure
nucleoside: consists of a nitrogenous base either pyrimidine or purine, and a sugar either ribose found in RNA or deoxyribose found in DNA. Does not contain a phosphate group e.g Adenosine
nucleotide: is a nucleoside with a phosphate group attached to it. it is the basic unit of nucleic acids like DNA or RNA
Nucleic acids vs nucleotides
nucleic acids are macromolecules that are long polymers made up of individual monomer units called nucleotides (polynucleotides).
Nucleotides are bound together by
Phosphodiester bonds
In nature the two main types of nucleic acids are
DNA and RNA
Process of replication
DNA carries genetic information that is inherited and passed down through generations through cell division
Process of transcription and translation
DNA uses part of its genetic information (genes) which are read (transcribed), by converting the code into RNA and then translating the genetic code (from nucleotides to amino acids) to make important proteins from cells to function
Nucleic acids is a genetic blueprint
each gene = word
each nucleotide = letter
polynucleotides
nucleic acids exist as polymers
Polynucleotides consists of
monomer subunits called nucleotides
nucleotides are composed of
- nitrogenous base
- pentose (5 carbon sugar)
- phosphate group
nucleoside
molecule composed of nitrogenous base linked to 5-carbon sugar (no phosphate)
nucleotide
nucleoside monophosphate
base component of nucleotides
nitrogen-containing rings referred to as bases
2 groups:
purines (guanine G, adenine A) and pyrimidines (Cytosine C, Thymine T and Uracil U)
Sugar components of nucleotides
5-carbon sugar can be either ribose or deoxyribose
phosphate component of nucleotides
nucleotides may have either 1,2 or 3 phosphate groups attached to the 5-carbon (C5 OH) group (=5’) of the ribose or deoxyribose sugar
however, polynucleotides (polymer) in nucleic acids only have one phosphate
The phosphate component is a constant of a nucleotide
is also called a nucleoside monphosphate
Nucleotides containing
Ribose (ribonucleotides)
deoxyribose (deoxyribonucleotdes)
Therefore the nucleic acid RNA is made up of ribonucleotides and DNA is made up of deoxyribonucleotides
The sugar component is a constant for the type of nucleic acid
Each nucleic acid is named after the base it contains
the base component is a non-constant (they are what varies)
therefore nucleotides are labelled according to the base because the sugar and phosphate component of each nucleotide is a constant
nucleotides are abbreviated as capital letters
AMP = adenosine monophosphate
dAMP = deoxyadenosine monophosphate
UDP = uridine diphosphate
ATP = adenosine triphosphate
base and nucleoside
adenine -> adenosine A
guanine -> guanosine G
Cytosine -> cytidine C
Uracil -> uridine U
Thymine -> thymidine T
nucleic acid polymer chains are
synthesised from energy-rich nucleoside triphosphate (A,C,G, T or U)
In these processes of nucleic acid synthesis (DNA or RNA)
these nucleoside triphosphates are added to the growing nucleic acid polymer chain by specific enzymes that can catalyse phosphodiester bonding between adjacent nucleotides and two phosphates are lost resulting in nucleoside monophosphate = nucleotide
two main types of nucleic acid
Ribonucleic acid (RNA) and deoxyribonucleic acid (DNA)
Ribonucleic acid (RNA)
- Ribonucleeotides contain the sugar ribose
- Ribonucleotides contain 4 types of nitrogenous bases = A, C, G U
- Single-stranded ( one polymer of polynucleotides)
Deoxyribonucleic acid (DNA)
- Deoxyribonucleotides contain the sugar deoxyribose
- Deoxyribonucleotides contain 4 types of bases = A, G, C, T
- Double-stranded (two polymers bound together)
ribonucleotides
OH on carbon 2
1 phosphate always attached to
thymine turns into uracil
deoxy
O removed from the OH group on Carbon 2
Thymine instead of Uracil
5’ and 3’
(5 prime and 3 prime)
5 prime indicate the start of the strand as it bonds to the 5 carbon group
3 prime indicates the end of the code as it bonds to the 3 carbon group
always read from 5’ to 3’
nucleotides
(nt)
base pairing
only A-T or T-A and G-C or C-G
bonding between base pairs
bond type 1 found in all nucleic acids, holds each nucleotide together hold individual nucleotides together in a chain, polymer - phosphodiester bond
bond type 2 (hydrogen bond) occur between the base pairs, none in RNA as its single stranded, only in DNA
adjacent nucleotides (nt) are joined together by
covalent onds (phosphodiester bonds)
results in a backbone with a repeating pattern of sugar-phosphate units
phosphodiester bonds occur
between-OH group on the 3C’ of one nt and phosphate on the 5C’ of the next nt
2 free ends of polymer distinctly different from each other (chemical polarity):
one end: phosphate attached to 5C’ = 5’ end
Other end: -OH group attached to 3C’ = 3’ end
RNA molecules
single polynucleotide chain
DNA molecules
2 polynucleotide chains that spiral around an imaginary axis forming a double helix
2 hydrogen bonds
A=T
3 hydrogen bonds
G-=C
Thymine T
2,4-dioxo-5-methyl pyrimidine
Cytosine C
2-oxo-4-amino pyrimidine
Adenine A
6-aminopurine
Guanine G
2-amino-6-oxopurine
Uracil U
2,4-dioxopyrimidine
Pyrimidines
Thymine
Cytosine
Uracil
Purines
Adenine
Guanine
Purine always bonds
with a pyrimidine between two polymer strands through hydrogen bonds
Adenine (purine) forms
2 hydrogen bonds with thymine (pyrimidine)
Guanine (purine) forms
three hydrogen bonds with cytosine (pyrimidine)
A-T and C-G are known as
base pairs (bp) and bind by complementary base pairing (Chargaffs rule, 1950)
Therefore, given the sequence of bases on one strand of the DNA double helix, the sequence of the complimentary strand is fixed and easily determined
chargaff’s rule
- the amount of adenine A in DNA is always equal to the amount of Thymine T
- The amount of Cytosine is always equal to the amount of Guanine
DNA requires hydrogen bonding
between nitrogenous bases forming base pairs
Watson and Crick 1953
discovered the DNA helix and father of the human genome project (Dr James Watson) became the first human to receive the data encompassing his personal genome sequence at Baylor College of Medicine in Houston on 31st May 2007
Shared the Nobel prize in physiology or medicine, 1962 for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material
X-ray crystallography
the last piece of DNA puzzle
results:
DNA’s helical structure was composed of two strands
established that DNA’s diameter was similar throughout
calculated that 1 turn was 34 A, distance between base pairs as 3.4A and 10 nucleotides per helical turn
showed that sugar phosphate backbones were located outside of the structure
